Racercook315

I recently bought a lemon🖕 but the car has long tube headers with high flow cats and magniflow supers, a cold air intake, and a flash tune. I bought it with these modifications and i keep getting a lean and rich code on bank one that wont go away. Ive replaced spark plugs, coil packs and all 02 sensors. I have a small leak in my break boster so i thought it might be a vacuum leak but i sprayed the location with stater fluid and the idel didn't change. I also bought a laser thermometer and all the cylinders were reading 170 but cylinder 2 was reading 250. The car runs fine when i reflash the tune but once the computer relearns its self i get backfires. Could this be injectors or something else? The codes dont tell me if its an 02 problem all they read is bank 1 is reading lean and rich. This is my daily and i dont want to blow it up, please help 🙏

Bert

that's a new one for me; I don't understand how it can be both lean and rich at the same time . . . maybe an O2 sensor problem, throwing bad info to the computer which is making it schitzo

m05fastbackGT

Also doesn't make much sense here either.. The OP has either a rich or lean A/F condition, but not both at the same time

Bert

I guess if the O2 sensor signal was fluctuating like crazy, due to a bad sensor or a short or something, the computer might interpret it that way; and then go crazy trying to adjust up and down and back up again

m05fastbackGT

I suppose it could be possible

Racercook315

thats why im so confused on this because i dont know how it would read lean and rich. Just frome checking the cylinder temps i would believe the computer is just freaked out and the one cylinder is running lean.

shaneyusa

Yup having both lean and rich is confusing. Is it reporting the cylinders? Could it be a sensor combined with an injector problem for different cylinders? Or just a messed up ECU?

Racercook315

just a bank 1 lean and rich. Doesn't tell me wich cylinder or o2. Could a stand alone fix this? I. About to order injectors to see if that dose anything it's just 400 for 8🤢

houtex

First, welcome to the forums, belatedly.

Second... stop. Just... stop. Breathe. And don't panic. I'm going to be real here, and sound either condescending or jerk or whatever negativity you readers may think I'm bein', but sometimes harsh needs to happen.

This is a gigantic mess you've acquired, unfortunately, and it doesn't seem you have the knowledge or tools on hand, hence you're here. And that's fine! No worries, we're generally here to help. But the reality is this car's had stuff done, and apparently done wrongly (and maybe why it was sold? ) that really requires someone that knows what's happening, has the tools to look at it, diagnose it, and then properly fix it. This means taking it somewhere. And/or spending money to redo stuff or what have you.

What I'm reading you're about to do is load a very expensive parts cannon and shoot it. That's just not going to be the right call. You're going to spend a lot of money on it that you could spend with someone who knows what's what and fixes it for as much *or less*, even.

My point on all this is we can throw all kinds of theories and possibles and maybes and send you down primrose paths to nowhere, and all of it costing a lot of time, effort and money. Because we're all *waaay* over here (most likely) so we can't get hands on. Please don't start acting on any of that. Take it somewhere. You'll be happier about it.

Or sell it. That's an option. May be the better part of valor, if this modded by someone else is supposed to be your daily. Always go stock for that, not modded. Easier to fix, less chance of breakage, overall. Get the modded toy for later.

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As far as the problem, there's no way a bank reads lean and rich at the same time. Not possible. It's one or the other... at a time. Which leads me to believe it's a long term codes stored situation where the engine HAS been lean long enough, then somehow winds up being rich for long enough, so both codes get thrown and stored.

Lean is too much air/not enough fuel. So either injectors aren't squirting enough, or unexpected air is getting in somewhere. Injectors can be pulled and flow tested, cleaned, or replaced, but it's moot if it's an intake issue. I'd run a smoke test and see if the smoke escapes somewhere. (Please note, the cold air intake may not be tuned in your tune, so that may be where the problem lies too.)

Rich is too much fuel/not enough air. And while I'm sure it's possible there's an air restriction because of too much back pressure (cats plugged maybe? You should check that for sure anyway) it's more likely the injectors are tossing in too much fuel. Which contradicts the above lean situations.

Like I said, you acquired a giant mess.

Assuming (we know what this word means, right?) the intake's fine, the exhaust is fine, the injectors are fine, sensors, wiring, computers... ALL THE THINGS are fine... then the tune is junk and you need a new one that takes into account all the changes, as the one you have probably (siphons with a large amount of negative pressure).

I'd therefore at the end of it recommend you take it to a proper tuner/speed shop that can work on Mustangs of this era and get them to figure it out. Again, assuming all the parts are good. Which they may find and fix for you for a charge, of course. At the very least, for sure you need a proper scan tool that can dynamically live read all the conditions of the car to properly figure out what's actually wrong and attack it correctly.

Which may end up being the tune. Which is going to require a tuner/speed shop... circular argument commences.

And overall, the point of this rambling is this: I certainly wish you to not spend bad money on theories. Get good info, then attack properly. It's always cheaper and correct.

I do hope this helps. Good luck!

Bert

pretty sure "bank 1" or "bank 2" is referring to the O2 sensors and it can't tell any more than that because there are only two sensors, one on each side
so my best SWAG is still O2 sensor problem
you can visually check the wiring for free, if you can get under the car

houtex

No, bank 1 is the passenger side exhaust, bank 2 is the driver side. There's sensor 1 and sensor 2 in each, one upstream of the cat and one downstream. So it'll be Bank 1 Sensor 1 or Bank 2 Sensor 1 throwing a code.

Which does, however, bring up an excellent point... if Bank 1 Sensor 1 is showing rich and then Bank 2 Sensor 2 is showing lean, that IS a possible. Unlikely, but possible, sure. That's be sensors/wiring, and so yes, checking all that makes sense. Maybe it's a melted wire or something...

See? WAAAY over here issues. Can't see/hear it all correctly, so mistakes and stuff.

I had a flash thought, but then tossed it out, but then bring it back because... maybe? I offer it up for derisive pointing at me by everyone nonetheless: IF the rich is sensor 1, the lean is sensor 2, on the same bank, the cat is burning the excess fuel, so there ya go, goofiness of data solved!

But I sort of think that's not how that's going to work, really, unless they are some really efficient cats at burning excess fuel... And then destroying themselves from the resultant burning, because cats don't like faw fuel in them to that amount....

/Interesting thought process, me. I'm sure that it's completely stupid. - My brain.

Bert

yeah that's what I meant -- bank = side and corresponds to the O2 sensors which are 1 (or 2) per side

I'm pretty sure that, since the rear O2 sensors don't do anything except confirm that the cats are working, we can forget about them for this conversation. I am not 100% positive, but pretty sure, the rear O2 sensors do not give air/fuel mix info to the computer; or at least the computer does not do anything with that (A/F mix is controlled based on front O2 sensors

anyway it's kinda fun to exercise our brains with these puzzles, just in case we didn't have anything else interesting to think about, LOL